High Throughput Single-Cell Phenotype Isolation by Protrusion Analysis Chip (PAC) There is increasing evidence that solid tumors are likely comprised of many subpopulations of cells with distinct genotypes and phenotypes, which is a phenomenon termed intratumor heterogeneity. Such heterogeneity becomes a major obstacle to effective cancer treatment and personalized medicine. Because of this inherent heterogeneity, data collected from cancer cell population-averaged assays likely hides valuable but rare events such as dramatic variations in gene expression at the single cell level. Therefore, understanding cellular heterogeneity from cancer biospecimens, especially in the study of phenotype-genotype correlation, will facilitate identification of new cell subsets, and assist in cancer prevention, diagnosis, and therapy. In this proposal, we focus on developing a high throughput approach for single-cell isolation based on cells' capability in generating protrusions. To be able to retrieve the desired single adherent cell, a Protrusion Analysis Chip (PAC) is proposed, in which the single cell is captured by a single hook and physically isolated by a barrier. The PAC is rapid, operationally simple, highly efficient, and requires low-volume sample introduction. After adhesion and spreading, cell phenotype is identified microscopically and then the desired cell is retrieved for genotype analysis. The proposed technology developments and study plans may potentially strengthen the understanding of the relationship between phenotype and genotype at the single cell level.